My first year of med school, I played soccer for a club team at the University of Missouri. We were having a practice, and it was a beautiful day to be out and moving. I was playing striker up front, and as the goalkeeper cleared the ball, I twisted to reach it and then felt this popping sensation and incredible pain in my right knee. I dropped, screaming, "I tore my ACL, I tore my ACL!"

That "ACL" would be the anterior cruciate ligament, and I knew immediately it was torn. The hospital visit that day confirmed my self-diagnosis. But I was stubborn. I didn't have surgery right away; a funny thing about this kind of injury is that after a couple of weeks you feel pretty normal. 1 In the beginning I was hopeful: Maybe it wouldn't be so bad; maybe the tear would heal on its own. That's denial for you. But every time I twisted my knee after that, even a little bit, I felt it buckle. The joint was totally unstable. Still, that didn't stop me from playing basketball with my brothers. Then one day as I went for a layup, my knee gave out. I hobbled off the court, realizing I had to have this problem fixed.

What I didn't know at the time was that I could've been doing a whole host of preventive exercises that may have kept the original injury from happening. Later in life, when I got into plyometrics and strength training, I noticed that my knee felt better when I kept the muscles around it strong. When my hips, glutes, and legs were strong, my knee hurt less.

I had an amazing realization: I can control my pain with strength.

This is crucial information for every active guy, because strength training can not only prevent injuries in the first place, but also ease your symptoms if you do have a joint injury that causes some chronic pain. How? Muscles support and stabilize joints. Despite some meniscus tearing and osteoarthritis, I can now train for the highest levels of endurance competition without a problem. I've completed nine Ironman triathlons and 29 marathons since my injury. Think about that the next time you want to skip a workout or skimp on rehabbing what's hurting.

But I'll never forget how awful that injury felt, not just in my knee but also in my mind. When you're active and that's taken away from you, it's traumatic. That's one of the biggest reasons I went into medicine, and why I wrote this story. If you're in pain and don't know why, or even if you know exactly why, you need to figure out what to do about it. My goal is to help you do that. I want you back in the game ASAP.

PLAY AROUND THE PAINOne of the first things you hear when you hurt yourself is "R.I.C.E." That's a common sports-medicine acronym for "rest, ice, compression, and elevation." The conventional wisdom for a lot of sports injuries, especially strains and sprains, is to rest your body, ice the injured area a few times a day for the first 48 hours, apply compression (an elastic bandage, for example), and elevate the affected body part above your heart to decrease bloodflow, pain, and swelling.

Most of those work just fine—but I don't throw the term "R.I.C.E." around much. I thoroughly disagree with rest. (More on that in a moment.) Ice? I love ice. Ice is nature's anti-inflammatory. Compression and elevation work, too, but only on certain injuries. (Never compress a nerve-compression injury, for instance.) Put simply, the best treatments aren't always as universal as an acronym.

For me, healing is a two-step process. First, stop what you're doing. Second, keep going. And you're thinking: What does that mean?

It means that if you're hurt, stop the offending activity. And then start the real work. Let's be very clear: An injury does not grant you a vacation from fitness or exercise. You must continue to work out even if you need to take it easy on a particular body part so it can heal. There are specific reasons for this, and I've learned them firsthand as a doctor and an athlete. There are also smart ways to keep exercising without aggravating the body part that's been hurt.

But first, the why. Reason one is science based. More and more, doctors are moving away from recommending rest and toward encouraging injured patients to engage in physical activity. I'm one of those doctors. Take osteoarthritis, for example; the most common form of arthritis, it affects almost everyone by the age of 60. Previously, when a patient had a flare-up, we prescribed rest and medication. Now studies show that exercises that build muscle to help support and improve joint function, combined with weight loss, boost quality of life better than medication alone. As I said before: You can control pain with strength.

There's more. Being sidelined sucks. The feel-good neurotransmitters produced during exercise, like serotonin and dopamine, can act very much like drugs, making exercise our healthiest mind-altering activity. Having that hit taken away can be clinically depressing for people. This was exactly how I felt when I hurt my knee and couldn't exercise. That's why I believe that when you're hurt, rest is more than just unwise; it's medically unhealthy.

You need to work up a sweat to fight all those negatives I've just described. If you do, you'll keep some of your conditioning. You'll get your dose of neurotransmitters. You'll feel better. You'll be more positive. And you'll learn that no injury is the end of the world. Make this your mantra: Exercise is medicine. It's the easiest way to feel happy and healthy.

So how do you exercise while injured? Practice what I call "dynamic rest."

That means two things. The first is rest and rehab. Lay off the injured body part and do what's necessary to nurse it back to health. That could involve specific home remedies, like ice or stretching, or something prescribed by a doctor, like targeted physical therapy or exercises.

Second, be dynamic. Stay in motion amid all this rest and rehab. Here's how.

Exercise your options. If you sprain your ankle, for example, do something that doesn't load your ankle. Hit the pool. Focus on upper-body weight training. Bad knee? Same idea. Whatever your injury is, don't play through the pain; play around it. Bad shoulder or elbow? Run and do lower-body plyometrics. And here's a big one: Bad back? Simply move. Walk. Shuffle if you have to. Resting a bad back only deconditions the muscles and makes your back weaker. No matter which body part hurts, find something that doesn't aggravate it, and never, ever do "total rest."

Go hard at all times. Whatever your alternate activity is, jack up the intensity. You'll have your heart pounding and lungs heaving as you keep your cardiovascular system in shape. Heck, you might even improve it. You'll also release those giddy neurotransmitters, making you the happiest hurt person on earth.

BUILD AN INJURY-PROOF BODYTo prevent your next injury, I recommend starting now. And my most important advice is to train your entire body. Switch up your activities and hit all the muscle groups, even if you play only one sport. I teach weekend plyometric strength classes that involve functional body motion. I'm a huge fan of this; it trains your body for real-world movement. Back when I was rehabbing my knee, I'd do leg extensions and hamstring curls—isolated movements that have no basis in reality. Now I never use those machines. I do balance work, single-leg work, and plyometric exercises like lunges and squat jumps—movements that hit a lot of muscles at the same time and keep my body in balance.

Why does this work? It's all about your kinetic chain, which is jargon for the series of body parts—including muscles, ligaments, joints, and connective tissue from your neck to your feet—involved in a movement. Your kinetic chain operates interdependently as one system: feet muscles working with ankles working with calves working with knees working with quads, hammies, and hips—all the way up to the top. That's why total-body conditioning helps keep you injury-free: If it's a chain, what do you think happens around a weak link? Exactly. Muscle imbalances eventually cause injuries.

Here are some smart ways to increase your total-body conditioning, as well as hit areas that a lot of guys—even active guys—neglect.

Compound your exercises. Whenever you can, work multiple muscles with a single exercise. If you do a forward lunge, for example, do it holding a medicine ball and add a core twist. And after that forward lunge? Do a reverse lunge and side lunges as well. Hit all directions. That's how you achieve muscle balance.

Stay single. Do single-leg exercises. In my strength and conditioning classes, I have people do single-leg squats, single-leg hops, single-leg lunges—exercises that allow them to use their own body weight while also maintaining their balance. Once you add these exercises to your workout, you'll notice more strength and stability around your ankles, knees, and hips—your most vulnerable points.

Twitch it up. Depending on your sport, you may be doing this already. But if you're not—if you train for steady-state sports like running or cycling—try adding one or two total-body plyometric and interval (sprint) workouts each week. Neither requires a gym or any special gear. Why do this? It's vital to maintain a balance between fast-and slow-twitch fibers. You become more athletic and less prone to overuse injuries, and you keep your body ready for any type of challenge.

Join the women. Yoga and pilates, gentlemen, yoga and pilates. I can't recommend them enough. These disciplines deliver dynamic, movement-based flexibility that can transform your body. Pilates also hammers your core. You'll feel more powerful, and your movement will be easier and more fluid. When you have that going for you, it's harder to get hurt.

Feel kneaded. I'm a big believer in massage. It feels great, of course, but you're also keeping your muscles supple. Plus, a good massage therapist can feel where your muscles might be chronically tight and setting you up for potential problems down the road. Shoot for two massages a month.

Rehab in your sleep. If you take nothing else from this story, know that sleep is the most important activity of your day. This is a huge blind spot for so many people, especially if they're training hard. Sleep gives your body an opportunity to repair and rejuvenate itself as it rebuilds muscle, strengthens bone, restocks red blood cells, and engages in other crucial processes that take time. And good sleep means better athletic performance and less chance of taking a bad step in the first place

When Should You Call a Doctor?

A lot of sports injuries can be self-diagnosed and self-treated. But in these three instances, you should have a pro look you over.

1. You have any joint pain, swelling, or instability. If a joint hurts or swells—especially a knee, hip, shoulder, or elbow—see a doctor. But if the area also turns red and is warm to the touch, head to your doctor ASAP; you could have an infection.

2. Your injury involves loss of consciousness or memory. I'm talking about a possible concussion here, men. Don't be stupid. Even the most minor brain injury needs to be checked out by a doctor—not a buddy, not a coach.

3. The pain doesn't go away.

Even if you do no self-care whatsoever, just about any strain, sprain, or pain should show some improvement within a week to 10 days. If it doesn't—or actually worsens—then make the call and have the injury checked out.

3 DIY Ice Packs

It's the all-natural antidote for pain and swelling. Make your own ice pack quickly and easily, and then apply to your skin for 10 to 15 minutes.

THE SLUSHIEFill a zip-top freezer bag with three parts water and one part rubbing alcohol, and toss it in the freezer. The alcohol keeps the mixture from freezing solid, giving you a slushy, pliable ice pack.

THE WET BLANKETWet a small towel under the faucet, wring out the excess, and pop it in the freezer. In about 20 minutes you'll have an icy blanket that's perfect for wrapping around your neck or an injured joint.

THE SIDE DISHIn a pinch, a bag of frozen peas or mixed vegetables makes a terrific ice pack. Then, after they've spent 15 minutes on your aching knee, steam them for dinner!

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